The present invention relates to a method of operating a lathe and to supplemental equipment for that purpose.
A conventional lathe includes a headstock an a tailstock for holding a workpiece during, e.g., cutting; and the headstock is usually constructed to hold a chuck. A conventional chuck for a lathe incluces a, usually, cylindrical body to be secured to the drive flange of the lathe. The chuck elements or jaws are mounted to the chuck body for clamping one end of the workpiece in particular relation to the axis of rotation.
The most commonly used chuck includes three jaws which are mounted to the chuck body for adjustment along three radial lines spaced by a 120.degree.. A helical groove at the bottom of the chuck induces the jaws to undergo simultaneous motion so that the tips will always make a true circle. Each jaw has a tapered front end which points towards the common center of the three jaws. The front end is rounded or flat, but quite thin. These three tapered front ends engage a round workpiece in three, almost line-shaped surface portions and, thus, provide a mathematically three-point support (in any plane transversely to the axis of rotation) for the workpieces, the clamping forces being directed radially towards the common center through the axis of rotation of the lathe.
Another kind of chuck is used for rectangular-or square-shaped workpieces. This chuck includes four jaws, arranged in pairs, whereby the jaws of one pair are adjustable to each other along a first line through the axis of roatation, and the jaws of the second pair are also adjustable to each other along a line that is orthogonal to the first one as well as to the axis, and traverses the point of intersection of this axis and of the first-mentioned line.
It is, thus, apparent that if a lathe is to be used for both kinds of workpieces (round and rectangular), both kinds of chucks are needed. Aside from the fact that chucks are expensive, one has to exchange one for the other in between workings. U.S. Pat. No. 2,757,008 discloses an elaborate system for reconstructing the jaws of a three-jaw chuck, converting the system, in effect, into an arrangement of three master jaws, each supporting a modified jaw structure. This multiple component structure does not permit adaptation of a standard jaw structure.